There are a couple of people here who have had bad lobes, myself included. But you'll notice it way before 8 PSI. It'll sound weird and feel like you lost a cylinder even below boost.

Remove the rear valve cover and have someone crank the motor (you can pull the fuel pump fuse if you'd like, but it won't be too messy or anything, regardless). Watch the last two rocker arms from the driver's side, lobes 9 and 10. Those are the ones that go on these motors. If one of the rocker's isn't moving, you've got a problem.

Besides that, I would definitely try another ICM/set of coil packs. You can find them cheap on ebay sometimes off of newer 3400 or 3800s, I don't think they're any different.

That, and get a Delco O2 sensor in there. Bosch is junk for our cars.

If you are concerned about a bad lobe do a compression check to rule it out.  If it's worn it's usually on cylinder #5, lobe 10 or 11. 

Its more than likely something simple.  From what I understood about these cam failures, if it didn't happen before 50k miles it was unlikely to happen at all.  Check the plugs, or just replace them with R42LTS AC Delco plugs, they are real cheap. 

Good luck man.

Already have r42lts plugs in and they are new will do compression check this weekend

After checking the ignition, I would move on to the fuel pressure, might be running out of fuel and knock pulling timming out.  My turbo coupe did this from low fuel pressure at high boost.

Quote from: R Dubya on February 18, 2008, 06:25:53 PM
if it didn't happen before 50k miles it was unlikely to happen at all.

Mine went at 154k.

Did you have a lobe 10 failure?  I can't recall :icon_redface:

That comes from me talking about these engines with the techs at the dealer I was working at.. it's a general statement from one of them.  Obviously it's not 100% but when cams fail at 30k miles, it's a lot different than 150k.  It would be nice if it didn't happen at all! :laugh:

If you had a bad lobe the car would backfire, stall out intermittently, and it would also be pushing boost back through the intake (at least it was on mine). 

I swapped in a ICM and coils from my girlfriends old 3100 97 buick skylark gran sport.  They work fine, might not be the same pn but output and connections are probably the same.  Much like all GM fuel pumps the P/N change does not necessarily dictate a function change.  Try the coil and icm before you do anything else.

Ken

When you had the plenum off changing the fuel injectors, did you make sure that all the vacume lines didnt break and were installed correctly? Also, did you make sure to plug the PCV valve hose back in.

yes I replaced all the vacaum lines when I had the intake off. I am going to replace the ICM and coils hopefully next weekend. God I hope it fixes it.

if you are near an Autozone or Advance or many other places, they are capable of testing the ICM with the coils off and see if it fails. 

It is possible for one circuit to fail and prevent the firing of one coil, I've had it happen.  Before you drop the $100 bucks have them test it.